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.TH DAEMON 3C "Sep 15, 2009"
.SH NAME
daemon \- basic daemonization function
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>

\fBint\fR \fBdaemon\fR(\fBint\fR \fInochdir\fR, \fBint\fR \fInoclose\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBdaemon()\fR function provides a means for applications to run in the
background.
.sp
.LP
This function ensures that the process calling this function:
.RS +4
.TP
.ie t \(bu
.el o
runs in the background
.RE
.RS +4
.TP
.ie t \(bu
.el o
detaches from the controlling terminal
.RE
.RS +4
.TP
.ie t \(bu
.el o
forms a new process group
.RE
.RS +4
.TP
.ie t \(bu
.el o
is not a session group leader.
.RE
.sp
.LP
The arguments to this function are treated as boolean variables and are
evaluated using negative logic.
.sp
.LP
If the \fInochdir\fR argument is zero the working directory will be changed to
the root directory (/); otherwise it will not be.
.sp
.LP
If the \fInoclose\fR argument is zero the descriptors 0, 1, and 2 (normally
corresponding to standard input, output and error output, depending on the
application) will be redirected to \fB/dev/null\fR; otherwise they will not be.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBdaemon()\fR returns 0. Otherwise it returns -1
and sets \fBerrno\fR to the values specified for \fBfork\fR(2),
\fBsetsid\fR(2), \fBopen\fR(2), and \fBdup\fR(2).
.sp
.LP
If \fBdaemon()\fR is called with \fInoclose\fR set to 0 and fails to redirect
descriptors 0, 1, and 2 to \fB/dev/null\fR, those descriptors are not
guaranteed to be the same as before the call.
.SH EXAMPLES
.LP
\fBExample 1 \fRUsing daemon to run a process in the background.
.sp
.LP
The \fBmain()\fR function of a network server could look like this:

.sp
.in +2
.nf
int background;	/* background flag */

/* Load and verify the configuration. */

/* Go into background. */
if (background && daemon(0, 0) < 0)
        err(1, "daemon");

/* Process requests here. */
.fi
.in -2

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
_
MT-Level	Async-Signal-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR Intro (2),
.BR dup (2),
.BR fork (2),
.BR open (2),
.BR setsid (2),
.BR attributes (7)
